The elemental composition of the secretory granules of bovine adrenal chromaffin cells has been determined by a combination of electron energy loss spectroscopy and energy dispersive x-ray spectroscopy. Ultrathin cryosections of rapidly frozen cultured cells were prepared and transferred at -170 degrees C into the Hitachi H700H analytical electron microscope using a Gatan cryotransfer sample stage. Specimens were dehydrated in situ by warming up to -100 degrees C and spectra were recorded at this temperature to help minimize mass loss due to radiataion damage. Energy loss spectra were recorded in an attempt to determine the nitrogen-to-phosphorus ratio and hence to estimate the relative amounts of nucleotides, proteins and catecholamines in the granules. Energy dispersive spectra recorded at known dose were used to determine concentrations of potassium, calcium, chlorine, sodium and phosphorus. The results could be compared with existing data from isolated granules.